ULA Delta IV successfully launches NROL-47

United Launch Alliance launched a Delta IV rocket from Vandenberg Air Force Base, carrying the classified NROL-47 mission for the US National Reconnaissance Office. Following a scrub on Thursday, liftoff occurred on Friday at 22:10 UTC.

Most details of most NRO missions are classified – including the design, specification and capabilities of the satellites, their missions, orbits and operations. Despite this, amateur and professional observers have been able to infer many details from observation of the spacecraft and how they behave once in space, combined in some cases with classified information that has been leaked from government agencies and intelligence services.

By comparing public information about launches – such as notices to airmen (NOTAMS) and maritime warnings informing pilots and ship captains of hazard areas to those from previous missions – as well as considering the type of rocket and launch site being used – it is often possible to work out what type of satellite is being launched and what its mission will be before it lifts off.

NRO missions that normally use Vandenberg include optical imaging satellites, which use near-polar sun-synchronous orbits, radar imaging satellites which fly in retrograde orbits, orbiting the Earth from east to west, and signals intelligence satellites (SIGINT) in inclined low-Earth and elliptical Molniya orbits.

The NRO’s optical imaging satellite series, Crystal, uses very heavy satellites which are well beyond the capabilities of the Delta IV Medium+(5,2) rocket that is to perform this launch. This particular version of the Delta IV has only flown twice before – on both occasions delivering Topaz radar imaging satellites into their retrograde orbits.

NROL-47 is unlikely to belong to either of the two NRO SIGINT programs that launch from Vandenberg. The low-orbit constellation, Intruder, uses pairs of spacecraft launched together to pinpoint ships at sea from their communications. Intruder satellites have never launched on Delta IV, and none of the satellites in orbit are currently old enough to warrant a replacement launch. The Molniya-orbit system – which is known as “Further Improved Trumpet” or “Trumpet Follow-On 2” – as the actual name is not known – uses satellites that would be too heavy for the Delta IV-M+(5,2) to deploy.

NROL-47 Logo – via ULA

The Topaz radar imaging satellites are believed to have been developed under the NRO’s Future Imagery Architecture (FIA) program – which was to have replaced both the agency’s radar and optical-imaging fleets of satellites. The optical component of the program was canceled amid cost overruns and schedule delays; however, four radar satellites have now been launched – between September 2010 and February 2016.

Topaz replaced the previous-generation radar imaging system, Onyx, which had consisted of five spacecraft deployed between 1988 and 2005. Previously known as Lacrosse, Onyx used two planes of satellites at different inclinations: three satellites were placed in a 57-degree orbit, and the other two used a 68-degree orbit. So far all four Topaz satellites have been placed into 123-degree orbits, the retrograde analogue of the 57-degree orbit used by Onyx. Each satellite’s orbit is separated by 90 degrees in right ascension of its ascending node.

Budget documents leaked to the Washington Post by Edward Snowden in 2013 confirmed that Topaz was the name of the NRO’s new radar imaging constellation. A line item listed Topaz 1-5, while production of a Block II satellite was discussed elsewhere in the report, suggesting that the initial constellation would include five spacecraft.

Hazard areas published for the launch do not correspond to any orbit that has previously been used by the NRO. The rocket will fly along a south-westerly azimuth after departing Vandenberg, taking it out over the Pacific Ocean and into a retrograde orbit.

The trajectory takes the rocket further to the south than the rockets that carried Topaz satellites. Assuming the rocket does not perform a dog-leg maneuver to change its final orbit after clearing these hazard areas, this course would result in a lower-inclination orbit than the 123-degree orbits used by Topaz. Because the orbit is retrograde, this lower inclination means the satellite would pass over higher latitudes on the Earth’s surface.

On SeeSat-L, a mailing list that contains a community of leading amateur satellite observers, Marco Langbroek has calculated a likely destination orbit for NROL-47 based on the launch hazard areas and additional NOTAMS that show that the rocket’s second stage is expected to reenter off the coast of Antarctica about two hours and 23 minutes after launch. His calculations have shown a near-circular orbit at an altitude of 1,500 kilometers (930 miles, 810 nautical miles) and an inclination of 108.6 degrees.

The use of a retrograde orbit suggests that the satellite is still some form of radar imaging satellite – as there is little reason to put any other type of reconnaissance satellite into retrograde orbit. It is unclear why a different orbit is being used for NROL-47 – although this could be related to the 68-degree plane of the former Onyx constellation. A 108.6-degree orbit would give the satellite coverage of the same latitudes as a spacecraft in a 71.4-degree prograde orbit – allowing it to cover parts of the Earth’s surface that would not be visible to the four spacecraft already in orbit.

Another possibility is that NROL-47 is the first Block II Topaz, with the constellation adopting a different orbit, or that it is not a Topaz mission at all. This would leave no upcoming launch as an obvious candidate for Snowden’s “Topaz 5” spacecraft – however, the fifth satellite may have been a ground spare never intended to launch, or “Topaz 1” could have been a smaller prototype launched as USA-193 in 2006. The mission of USA-193, which failed immediately after separating from its Delta II carrier rocket, has never been identified but its orbital inclination was similar to that of an Onyx spacecraft.

More details will likely emerge once NROL-47 arrives on orbit and begins to be tracked by the amateur community. Once in orbit, the satellite will be renamed. Most US military satellites are given sequentially-numbered designations beginning with USA. Zuma was assigned the designation USA-280, so NROL-47 will probably be USA-281.

The launch made use of United Launch Alliance’s Delta IV Medium+(5,2) rocket. The launch, which marked the rocket’s thirty-sixth flight, had flight number Delta 379 (D379). The Delta IV, which first flew in 2002, is one of two Evolved Expendable Launch Vehicles (EELVs) operated by ULA, along with the Atlas V.

Delta IV ahead of launch – Photo by Derrick Stamos for NSF/L2

The company also operates the older Delta II rocket, which will be retired later this year. ULA has operated these three rockets since it was formed in December 2006 – with Delta II and Delta IV having been previously operated by Boeing and Atlas V originally developed by Lockheed Martin.

The launch was the first Delta IV mission to use United Launch Alliance’s Common Avionics system, a standardized avionics package designed to be used on both the Atlas V and Delta IV rockets. By standardizing this component across their fleet, ULA aims to reduce costs and ensure a continued high level of reliability for both rockets. The NROL-47 mission was delayed from December in order to allow further checks to be carried out on the rocket’s new avionics.

Delta IV is a two-stage rocket, with an all-cryogenic core vehicle – fuelled by liquid hydrogen propellant and liquid oxygen oxidizer. The first stage is a Common Booster Core (CBC), powered by a single RS-68A engine. In the Medium+(5,2) configuration this is augmented by two GEM-60 solid rocket motors.

About five and a half seconds before liftoff, Delta 379 lit its RS-68A engine. Once the count reached zero, the two booster rockets ignited, and the Delta IV began its ascent towards orbit. The rocket took about fifty seconds to reach a speed of Mach 1 – the speed of sound – and passed through the area of maximum dynamic pressure (Max-Q) about twelve seconds later.

Delta IV launch – via ULA

The two GEM-60 motors burned for about 100 seconds before they burnt out. The spent casings were jettisoned ten seconds later. After climbing above the dense lower layers of the atmosphere, Delta 379 shed its payload fairing around three and a half minutes after liftoff. This was the last event before the mission enters a blackout, with no further information being released about its progress except a brief statement later confirming the successful completion of the launch.

The CBC will likely continue to burn until about four minutes and six seconds into the flight. Six seconds after shutdown, the first and second stages will separate. Delta’s second stage, the five-meter (16.4-foot) diameter version of the Delta Cryogenic Second Stage (DCSS), will begin to deploy the extendible nozzle of its RL10B-2 engine, with ignition coming about 13 seconds after separation.

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The second stage will probably make two burns to place the NROL-47 payload into its planned orbit. The timings of the upper stage burns are more mission-specific than earlier flight events and have not been published, however, the first burn is likely to be longer, typically around twelve-and-a-half minutes in duration, establishing an initial parking orbit. Following a coast phase, a much shorter second burn will circularise the orbit. This burn could take as little as fifteen seconds.

Spacecraft separation will occur a few minutes after the end of the second burn. Once its primary mission is complete, the DCSS will make a final burn to deorbit itself.

Mission success was confirmed by ULA boss Tory Bruno in his traditional style, via the number of ULA success to date.

Delta IV can fly in several different configurations to suit different types of payload. The smallest version, the Delta IV Medium, consisted of a CBC with no additional solid motors and a four-meter (14.1-foot) DCSS. The three intermediate Medium+ configurations are the M+(4,2), with a four-meter DCSS and two GEM-60 boosters, the M+(5,2) that will be used for this launch, and the M+(5,4) which increases the number of GEM-60 boosters to four.

The most powerful version of the rocket is the Delta IV Heavy, which uses three Common Booster Cores, burning together at liftoff, to deliver the heaviest payloads to orbit. In its Heavy configuration, the Delta IV is currently the most powerful rocket in service worldwide – a title it will relinquish when SpaceX’s Falcon Heavy makes its debut.

United Launch Alliance is in the process of phasing-out the Delta IV in favor of its Atlas V product line, as the company begins the transition to its next-generation rocket, Vulcan. The single-core configurations are being retired first, with the Delta IV Heavy to continue flying in the near-to-medium-term as it is the only rocket both qualified and capable of deploying the United States’ largest national security satellites. The Delta IV Medium has already been retired, while each of the Medium+ configurations has a single launch remaining. This was the last launch to use the Medium+(5,2) version of the rocket.

In line with ULA’s plan to retire the Delta IV, the launch was also expected to be the last flight of a single-core Delta IV from Vandenberg Air Force Base. The remaining M+(4,2) and M+(5,4) missions – which will carry GPS and WGS satellites respectively – will take place from Cape Canaveral on the Eastern Range. The three-core Delta IV Heavy will continue to fly from both coasts, with its next Vandenberg launch scheduled for September with NROL-71 – likely a large electro-optical imaging satellite.

The Delta IV launch pad at Vandenberg is Space Launch Complex 6 (SLC-6). The complex was originally constructed in the 1960s for polar-orbit launches of the US Air Force’s Manned Orbiting Laboratory (MOL) space station atop Titan IIIM rockets, however, this project was canceled in favor of unmanned reconnaissance satellites before any missions could be launched.

Later the pad was rebuilt for the Space Shuttle, which was to have made its first west-coast launch in 1986. Following the loss of Challenger, Shuttle launches from Vandenberg were abandoned and the complex again went unused.

The first launch from SLC-6 finally took place in August 1995, with the maiden flight of the Lockheed Launch Vehicle (LLV) – later named Athena. Four Athena rockets launched from SLC-6 between 1995 and 1999. SLC-6’s first Delta IV launch was made in June 2006, with this mission the seventh Delta IV, and the eleventh launch overall from the pad.

The launch of NROL-47 was the first flight of 2018 for United Launch Alliance, the second of the year for the United States and the third worldwide. The launch came as part of a busy start to 2018 for spaceflight, with ten planned launches in twelve days beginning on Monday with SpaceX’s launch of Zuma atop a Falcon 9. ULA will be in action again on 19 January, with an Atlas V flying from Cape Canaveral to deploy the SBIRS GEO-4 missile early warning satellite.

The launch was the first of four Delta IV missions planned for 2018. The next is currently targeting 31 July, with a Delta IV Heavy due to loft NASA’s Parker Solar Probe on a mission to study the Sun. Another NRO launch – NROL-71 – is scheduled for September using a Delta IV Heavy, while the US Air Force’s WGS-10 communications satellite will be launched by the last Delta IV Medium+(5,4) in early November.

NROL-71 is currently the next scheduled mission for the NRO – although another mission, NROL-111, is also expected late in the year and a date has not yet been announced.